Statement of the Technical Field
The disclosure relates to reaction thrusters (e.g., Hall or ion thrusters). More particularly, the disclosure concerns systems and methods for ground based testing of reaction thrusters intended for use in low density and pressure environments (e.g., outer space, or an altitude greater than 122 km).
Description of the Related Art
There are many reaction thrusters known in the art, such as ion thrusters. Ion thrusters are generally used to propel a craft by accelerating ions. A Hall Effect type ion thruster comprises an electrode inside of a discharge channel (anode), a downstream cathode to provide electrons, and an applied mostly “radial” magnetic field topology in the discharge channel. The magnetic field topology is established by a magnetic circuit and a ferromagnetic structure. The magnetic circuit is composed of either electromagnetic coils or permanent magnets. The ferromagnetic structure behaves as flux channels for the magnetic fields generated by the field sources. An axial electric field is developed between the anode, which also can function as the neutral propellant distribution system in the discharge channel, and the electron emission source (cathode). Electrons emitted from the cathode are attracted towards the anode due to the potential gradient applied between the cathode and anode. The electrons that are accelerated towards the anode enter the discharge channel where they begin to experience an azimuthal ExB drift, creating what is referred to as the Hall current. The Hall current effectively impedes the majority of the axial electron motion towards the anode. The Hall current region forms what is described as a “virtual cathode”. The trapped electrons gyrate azimuthally around the discharge channel until they are either lost to the walls or anode, recombined, or involved in an ionization collision with neutral propellant particles flowed from upstream of the Hall current region. The ionized propellant gas then accelerates through the potential gradient maintained by the Hall current. The accelerated ion beam pulls additional electrons from the cathode into the ion beam to form a quasi-neutral propulsive plasma.
In some scenarios, ion thrusters are used to control the orientation and position of objects orbiting the earth (e.g., satellites). Accordingly, ion thrusters are designed to operate in a low density and pressure environment. Prior to deployment in such an environment, operation of the ion thruster is tested in a test environment. The test environment is intended to mimic the low density and pressure environment. In this regard, the test environment is created using a vacuum chamber (i.e., an enclosure from which air and other gases are removed by one or more vacuum pumps). The vacuum chamber is often formed of a conductive material (e.g., steel) which is typically connected to earth ground.